Method for applying and metal coating composition of a butadiene resin and organic derivative of titanium



March 1959 L. A. HENDERSON 7 METHOD FOR APPLYING AND METAL COATINGCOMPOSITION OF A BUTADIENE RESIN AND ORGANIC DERIVATIVE OF TITANIUMFiled March 15, 1956 HEAT-OURED ORGANIC TITANATE IODiFlEO BUTAOIEREPOLYMER OOATINO I FERROUS SHEET METAL Im PLATED I FERROUS nsm BODY sumOURED ORGANIC 5% TITANATE HOD- IFIED BUTAHENE ORGANIC TITAR- f ATEMODIFIED ii BUTAOIENE POLYMER TOP COAT.

iii;

TIN PLATED FERROUS IETALENO OSURE INVENTOR LORAN A. HENDERSON E Mam A il l United States Patent METHOD FOR APPLYING AND METAL COATINGCOMPOSITION OF A BUTADIENE RESIN AND ORGANIC DERIVATIVE OF TITANIUMLoran A. Henderson, Drexel Hill, Pa., assignor to E.' I. du Pout deNemours and Company, Wilmington, DeL, a corporation of DelawareApplication March 15, 1956, Serial No. 571,859

17 Claims. (Cl. 220-64) This invention relates to coating compositionsand more particularly relates to coating compositions designed for 1Although only a small fraction of the sheet metal used' in thefabrication of the tin can is tin, for example, about 0.25 to about 1.5pounds of tin per 218 square feet of surface area of an iron or steelmetal sheet, the tremendous consumption of tin for container use hascreated a significant shortage of tin in view of the known limited Worldsupply.

One method. of conserving tin has been tominimize the thickness of thetin coating and supplement it where necessary with a superimposedprotective organic coating, such as an oleo resinous varnish baked onthe ferrous sheet metal substrate. Such organic-coated, tin-platedferrous metal sheets are fabricated into interiorly coated metalcontainers which are particularly designed for packaging wet-pack foodproducts which are heat-processed or pasteurized in the container indirect contact with the organic coating.

Organic coatings which are useful'for this protective service must beinnocuous, free from components which alter taste and odor, resistant toaqueous extracts of the wet-pack food products under the conditionsassociated with heat-processing or pasteurization and during lengthystorage of the packaged food in the container.

High speed operations of container fabrication from the precoated sheetmetal imposes other important qualifications on candidate organiccoatings. A particularly important qualification is that the curedorganic coating must be adequately flexible to be fracture-resistantunder the conventional mechanical operations associated with stamping orcutting container body and end-closure parts from the precoated sheetmetal and fabricating the container parts into an interiorly coatedcontainer. The organic coating must also be adequately flexible to befracture-resistant under the heat and pressure conditions to which thecoated container is subjected during heatprocessiug of the foodproducts;

Lack of fracture-resistance is a common failure in many potentiallyuseful coatings and when these coatings are modified to improve theflexibility to provide adequate fracture-resistance, they ordinarily aredeficient in the properties pertinent to food-processing.

2,875,919 I Patented Mar. 3, I959 containers. A more specific object isthe provision of a butadiene polymer coating composition, which appliedat an effective protective thickness on sheet metal container parts, isadequately flexible to be resistant to fracturing under the mechanicaloperations involved in fabricating an interiorly coated container fromthe precoated parts. Another important object is the provision of ametal container, having on the interior surface thereof, a protectiveorganic coating which is fracture-resistant under conditions of metalexpansion and contraction caused by heat processing of wet-pack food andbeverage products in the container. A further object is to provide theaforementioned type'of container the'interior coating of which isphysically and chemically resistant to attack by the aqueous extracts ofsuch food and beverage products processed and stored in direct contactwith the protective organic coating. Still another object is to providea method of protectively coating a metal sheet substrate used in thefabrication of interiorly coated metal containers designed for use inthe packaging of wet-pack food and beverage products.

The objects of this invention are accomplished by applying to at leastone surface of a ferrous metal sheet substrate a liquid coatingcomposition comprising (A) 'a' butadiene polymer selected from the classconsisting of (1) homopolymers of butadiene-1,3,. (2) copolymers ofbutadiene-1,3 and styrene'and (3) said homopolymers and said copolymersmodified with an anhydride of an unsaturated dicarboxylic acid selectedfrom the class consisting of maleic anhydride and citraconic anhydrideand (B) at least one substantially non-volatile, organic solventsolubleorganic derivative of titanium selected from the class consisting of (l)orthotitanate esters of aliphatic monohydric alcohols, (2) orthotitanateesters ,of 2,3-diorgano-substituted 1,3 diols, (3) orthotitanate estersof enolizable beta-ketoacid esters and (4) titanium acylates of fattyoil acids; and heating the coated substrate to .cure the coating thereona I The accompanying drawings illustrate utility of the inventioncoating compositions as a can coating wherein:

Fig. l is a cross-sectional view of a flat sheet of tinplated ferroussheet metal of the type used in the fabrication of tin cans, the metalsubstrate having a heat-cured coating thereon comprising butadienepolymer and an organic titanate.

Fig. 2 is a cross-sectional view of a tin-can consisting of acylindrical body shell and an end-closure sealed thereto; the bodyshell, being fabricated from the precoated sheet metal described in Fig.l and having the heat-cured coating as an interior lining or base coat.

Fig. 3 is a cross-sectional view of a tin-can corresponding to thearticle in Fig. 2 further having a heat-cured superimposed coatingcomprising a butadiene polymer and an organic titanate, the top coatbeing applied after the seam of the base-coated body shell was solderedand an end-closure was sealed to one end of the body shell.

The following specific examples are given by way of illustration and notlimitation. The partsand percentages throughout the specification andclaims are expressed on a weight basis unless stated otherwise.

Example 1 Parts by wt. Butadiene polymer 42.50 Mineral spirits (B. R.145 C. to 215 C.) 56.63 Tetra(2-ethylhexyl) orthotitanate .85 Siliconefluid-General Electric SF-03 .02

teachings of Miller U. S. Patent 2,708,639 in which procbutadienepolymer was predissolved in the mineral spirits and thereafter the othercomponents of the composition were added and mixed until theproduct wasuniform.

This product was applied by flow-coating to one surface of a sheet of.25 electrolytically tin-plated steel, that is, the sheet steel had atin plating thereon corresponding to .25 pound of tin to about'218square feet of metal sheet surface, and partially dried by volatile lossof mineral spirits from the wet coating. Thereafter the coated ferrousmetalsheet was heated in an oven for 10 minutes at 385 F. to cure thecoating. The cured coating at a preferred dry coating weight of 5.5milligrams per square inch of surface was pale golden color, clear,transparent, adherent to the metal substrate, and continuous, that is,free from eye-holing or islands.

The sheet metal stock coated with the cured product of Example 1 wasstamped into container body parts and container end-closures forsubsequent fabrication as a cylindrical metal container having the metalsurface coated with the cured organic coating as the interior surface ofthe container.

Representative samples of'the stamped container parts were examined forcoating fracture which may be caused by the mechanical operations ofstamping the coated metal sheet. Because fracturing is not easilydetected by the unaided eye, fracturing was conveniently determined byaconventional chemical test used by the conta'iner industry in which thetest part is immersed in a copper sulfate plating bath for 10 minutesduring which time the copper sulfate electrolyte will penetrate throughany fractures to stain and plate out copper on the metal substrate atthe fractures in the coating.

A'suitable electrolyte bath for this test consists of 750 grams of CuSO-5H O and 190 grams of commercial concentrated hydrochloric acid dilutedto one gallon with distilled water.

In. carrying out the test, exposed metal and surface areas other thanthe test area were protected with a paratfin coating. applied as ahot-melt. After immersion inthe electrolyte, the test parts were rinsedwith water and examined for evidence of staining or copper plating. Thetested container parts coated with the product of Example 1 weresubstantially free from copper staining, indicating excellent resistanceto fracturing under the mechanical operations of container fabrication.Fracture-resistance was superior to that ordinarily accepted by thetrade as representative of organic coatings in commercial use for cancoating.

The coated container parts were fabricated as a container constituting'acylindrical body part with a soldered side seam and an end-closuredouble-seamed to the body part with the coated surfaces of the metalconstituting the interior surface of the containers. The resultinginteriorly coated-containers were tested by actually heatprocessingrepresentative wet-pack food'products in the container in direct contactwith the organic coating accordingto established test methods used bythe container industry. Sour .cherries, pumpkin, corn and pork were usedas representative food products in the processing tests. Depending onthe particular processed food product, heat-processing was carried outin a steam pressure cooker under conditions ranging from about 15minutes at 210 F. to 150 minutes at 250 F. with the pressure as high asthat corresponding to steam at a temperature within the indicated range.Each of the hermetically sealed food-filled containers had about onequarter inch of head space as air.

All the test containers having a content of processed food products wereimmediately cooled to room temperature after heat-processing and storedfor at least 18 hours before representative sealed containers wereopened for initial examination. Other series of hermetically sealed testcontainers filled with processed food were stored for subsequentinspection after periods of 1, 2 and 3 months storage at roomtemperature and storage at F.,' and after 1, 2 and 4 weeks storage at F.

After the respective storage periods, the containers were opened and theinterior surfaces thereof were examined for blistering, blushing,discoloration or staining, adhesion to the metal substrate, flaking andsoftness. In the initial examination after heat-processing of wet-packfood in the container, examination was also made for fracturing of thecoating as may be caused by expansion and contraction of the metalcontainer during processing of the food.

The cured coating of the product of Example 1 was resistant to physicaland chemical attack by aqueous extracts or juices of wet-pack foodproducts during heatprocessing in the container and during therespective storage periods of such food extracts and parent foodproducts in direct contact with the organic coating. The coating wasblush-resistant and blister-resistant. For all practical consideration,the coating was unchanged from its initial quality in reference tohardness, flexibility, color, clarity and adhesion. Slightsulfur-staining was detected on the interior surface of containers inwhich pork was heat-processed and stored. The coating exhibitedadvantageous improvement in reference to fracture-resistance andphysical and chemical resistance to aqueous food extracts and to theconditions associated with heat processing of the wet-pack food incomparison with a conventional oleoresinous varnish used to interiorlycoat food containers in the same described manner. There was no evidenceof deleterious effect of heatprocessing and storage on the food packagedin the test containers. 7

The product of Example 1 offered an additional advantage in that it wasadequately cured at a temperature at least 25 F. lower than that used tocure conventional oleoresinous varnishes designed for can coating, whichvarnishes ordinarily are cured by baking at a temperature of about 410F.

Comparable results were obtained in reference to fracture-resistanceduring mechanical operations and physical and chemical resistance underfood processing operations and during storage, when the product ofExample 1 was applied to other sheet steel having a surface coating oftin thereon ranging from .25 to 1.5 pounds per 218 square feet ofsurface, applied either electrolytically or by hot-dip, and theresulting organic-coated metal substrates were fabricated as aninteriorly coated container.

Example 2 Parts by wt. Butadiene homopolymer (same as used inExamcomposition .of the product .of this example is similar to that ofExample 1, but it includes tri(2-ethylhexyl=) orthophosphate, which inaddition to its plasticizing :effect functions to accelerate the cure ofthe product on heating, a d additional hydrocarbon diluent of thexylolsubstitute type high solvency petroleum naphtha to provide asprayable product.

The several components of the composition were mixed until the productwas uniform.

Metal containers were fabricated from container parts precoated with theproduct of Example 1 applied as described at a dry coating weight ofabout 3 milligrams per square inch of surface and cured by heatingminutes at 385 F. The resulting interiorly coated containers werefurther coated by spraying on their interior surfaces the product ofExample 2 which was applied at a dry coating weight of about 5milligrams per square inch of surface to provide a total dry coatingweight of about 8 milligrams per square inch. The final coating wascured by heating the coated container for 10 minutes at about 300 F.Representative containers of this type were filled with beer, sealed andsubjected to conventional pasteurization by heating for 30 minutes at150 F. Examination of the interior surface of representative containersopened 24 hours after pasteurization and after $.months of storagerevealed that the protective coating was unaffected by pasteurizationand storage in contact with the aqueous alcoholic malt beverage. Thequality of thestored beer was not distinguishable from samples of thesame beer bottled in glass.

The product of Example 2 was similarly applied by spraying to plainsheet steel, which did not have a surface coating of tin, at variouscoating weights ranging up to about 10 milligrams dry weight per .squareinch of coated surface and was cured under conditions ranging from '60minutes at 250 F to 5 minutes at 420 F. The resulting cured coatingswere found to be fracture resistant and flexible. Curing under theserespective conditions was found to provide substantially the same degreeof cure as accomplished by heating the coated substrate at 385 F. for 5to minutes.

Organic coated plain sheet steel is not used in the fabrication ofcontainers designed for wet-pack food packaging because the coatingweight of protective organic coating ordinarily applied over tin-platedsheet steel is not adequately protective against aqueous food extractsin the absence of the tin-plating which is at a coating weight of atleast about 25 pound of tin per 218 square feet of surface. Coatingweights of the butadiene polymer coating composition greater than 8milligrams dry weight per square inch can be satisfactorily applied toplain sheet steel to provide adequate protection against food-processingconditions, but application of a multiplicity of coats ordinarily isrequired to provide such higher coating weights. At the conventionalcoating weight of about 2 to 8 milligrams dry weight per square inch ofsurface applied to plain sheet steel, the organic coated sheet steel canbe fabricated into satisfactory containers which have general utilityexcept for packaging wet-pack food products.

Because processing of pork and corn ordinarily cause some staining ofthe interior surface of the container due to the sulfur content of thesefood products, it is desirable to include in the coating asulfur-sequestering agent, such as zinc oxide, which sequesters thesulfur in an apparently non-staining or non-discoloring form. Sulfursequestered as zinc sulfide is visually indetectable in the presence ofzinc oxide. Example 3 below is representative of using zinc oxide as asulfur sequestering agent in the invention compositions.

The zinc oxide was dispersed in the hydrocarbon solution of butadienepolymer in accordance with a conventional method of dispersing pigmentin paste form.

In the preparation of the product of Example 3, the components weremixed until the product was uniform. The zinc oxide content of theproduct was about 12.7% by weight based on the polymer content.

The product of this example was flow-coated on electrolytic tin-platedsheet steel in the same .manner as described in Example 1. The coatedmetal .sheet was fabricated into an interiorly coated containerand thecon tainer and parts thereof were tested as described above. Theresulting containers were found to be fully acceptable for packagingwet-pack .food products which are heap processed ,in the container. Theresults in the specific tests were equivalent to those obtained with theproduct of Example 1, with the added advantage that the interior coatedsurface of the container was resistant to sulfur-staining by pork andcorn products,

Example 4 Parts by wt. Butadiene polymer-Butarez #25 oil 40.0 Mineralspirits (B. R. C. to 215 C.) 57.0 Octyleneglycol titanate--Du PontsOGT-41-solution. 69% by wt. in butanol 3.0

The several components of the composition were until the product wasuniform.

The Butarez 25 oil, commercially available from Phillips PetroleumCompany, was a homopolymer of butadiene-1,3, having an average molecularweight of about 11500. The octyleneglycol titanate OGT-41 was thecommerciallyavailable tetra ester of orthotitanic acid and2-ethylhexanediol-1,3 described in Du Pont Titanium 50rganicsTitaniumChelates.

The product of this example was flow-coated on electrolytic tin-platedsheet steel at a dry coating weight of about 5 milligrams per squareinch and cured by heating the coated sheet metal for 10 minutes at 385-F. -The organic-coated sheet metal was satisfactorily fabricated intointeriorly lined containers which in turn were found to be entirelysatisfactory as containers designed for use in packaging wet-pack foodproducts. Fracturing tests and food processing tests yielded resultswhich were comparable with those obtained with the product of Example 1.

mixed Example 5 Parts by wt. Butadiene polymer-Butarez 25 oil 40.0Mineral spirits (B. R. 145" C; to 215 C.),- 57.3 Octyleneglycoltitanater-Du Ponts 0GT21 solution. 76% by wtcin butanol- 2.7

7" This product was identical incomposition with that of Example 4except that the titanate OGT-21 was substituted on an equal weighthasis'for OGT-41. OGT-Zl was the commercially available chelatedtitanium ester prepared by alcoholysis of tetrabutyl titanate in theproportion of one mol of the 'tetrabutyl vtitanate per two mols of-2-ethylhexanediol-1,3.' Hence, this 'chelated titanium derivativecontained a pair of butoxy substituents in addition to the two chelatedsubstituents per titanium atom.

Evaluation of this product yielded results which were identical withthose obtained with the product of Example 4.'

' Example 6 Parts by wt. Butadiene homopolymer-(same as used inExample 1) 37.50 Mineral spirits (B. R. 145 C.,to 210 C.) 59.48

Tetra(2-ethy1hexy1) Orthotitanate Solution-50% by wt. in Z-ethylhexanol1.50 Ethylacetoacetate 1.50 Silicone fluid--General Electric SF-03 .02

The components of the composition were mixed until the product wasuniform.- In this composition a titanium chelate was formed in situ byester interchange between the tetra(2-ethylhexyl) orthotitanate and theenolizable ethylacetoacetate, a betaketoacid ester. I Evaluation of theproduct of Example 6 as an interior coating'for food-processingcontainers as described in Example 1- yielded excellent results whichwere equal to thoseobtaind with the products of the preceding ex-'amples.

Example 7. Parts by wt. Butadiene polymerButarez 25 oil 40.0 Mineralspirits (B. 'R. 145 C. to 215 C.) 58.0 Polymeric isopropoxytitaniumoleate 2.0

The components of the composition were mixed until the product wasuniform. 'The polymeric isopropoxytitanium oleate was the commerciallyavailable TROLA isopropoxytitanium oleate described in Du Pont TitaniumOrganics-Titanium Acylates. This titanium acylate contains an average ofabout oneacylate group per titanium atom, the remaining substitue'nts onthe titanium atoms being isopropoxy groups. Theprodu'ct of thisexamplewas applied by flow-coatingon electrolytic tin-plated sheet steelto the preferred dry coating weight of about milligrams per square inchof coated surface and evaluated as an interior coating for containersused in wet-pack food packaging and heatprocessing as described inExample 1. The product was found to be suitable for can coating andthe'individual tests showed that the containers coated therewith weresignificantly better than containers interiorly coated with conventionaloleoresinous varnishes.

-'In the preparation of this product, the oily butadiene polymer was runto a temperature of 210 F. in 30 minutes, the maleic anhydride wasslowly added to the hot-oil while the temperature was raised to 300 F.in ZO i'ninutes and the mixture was vigorously agitated whilethe'tempe'rature was held at 300F. for 45 additional minutes.Thereafter, the mixture was cooled by dilution with the, mineral spiritsand the tetra(2-ethylhexyl) orthotitanate was added and uniformly mixedinto the composition to complete the product.

This product was flow-coated and cured on electrolytic. tin-plated sheetsteel as described in Example 1 and, in

turn, fabricated as an interiorly coated containers The.

container parts were examined for fracturing and the resulting containerwas evaluated as previously described for heat-processing of wet-packfood products. Containers interiorly coated with this product were foundtobe equivalent to those coated with the product of Example 1.

Citraconic anhydride substituted on an equal weigh't basis for themaleic anhydride in the preparation of the product of Example 8 providesa coating composition equally suitable for use 'in interiorly coatingcontainers for food packaging.

Example 9 Parts bywt. Butadiene/styrene copolymer 43.5 High solvencypetroleum naphtha (B. R. C.

to 195 C.) 28.2 Mineral spirits (B. R. C. to 215 C.) 27.0Tetra(2-ethy1hexyl) orthotitanate 1.3

The copolymer had a molecular weight of about 1200 and contained about90.8% by weight ofpolymerized butadiene-1,3 and 9.2% polymerizedstyrene, the polymerization being carried out in the presence of sodium/naphthalene catalyst. 1

The product of this example applied to a tinplated ferrous sheet metalsubstrate and evaluated as previously described in Example 1 was foundto be adequately fracture-resistant and flexible and suitably resistantchemically and physically for use as an interior coating of containersdesigned for packaging food products which ordinarily are heat-processedin the container.

Commercially available Standard Oil Companys .C, Oil, a copolymer ofbutadiene-1,3 and styrene comparable to that used in Example 9,substituted on an equal weight basis for the copolymer in that exampleprovides a product which is equivalent in quality when evaluated as aninterior can coating. This copolymer substituted on an equal weightbasis for the Butarez 25 Oil, butadiene homopolymer, in Example 8 andtreated with maleicanhydride as described therein provides an equivalenproduct suitable for container coating. v

As indicated'by the examples, a Wide variety'of butadiene polymers canbe used in the practice of this invention. Useful polymers includehomopolymers of butadiene-l,3 prepared by polymerization catalyzed byeither sodium, boron trifluoride, boron trifluoride etherate complex orboron trifluoride ethcrate complex and water. These homopolymers can beprepared by either a single stage process or by a. two-stage process inwhich the preformed polymer is subjected to further treatment with aFriedel-Crafts catalyst as described in Garber U. S. Patent 2,560,164 orsubjected to heat-bodying. Copolymers of butadiene-1,3 and styrene inwhich the butadiene-l,3 component is at least 75% by weight of thecopolymer can also be used. Preparation of useful.

copolymers of this type is described in Gleason U. S. Patent 2,672,425.These homopolymers and copolymers treated with either maleic anhydrideor citraconic anhy dride in an amount ranging up to about 2% based onthe weight of the polymer can also be successfully used in the practiceof this invention. Acid anhydride modified butadiene polymers of thistype are described in Gleason U. S. Patent 2,652,342 and in Miller U. S.Patent 2,708,639. Modification with the acid anhydride can be carriedout either as an after-treatment of'the'pr'easme oro formed polymer orduring the polymerization of the butadiene polymer. Polymers ofbutadiene in which the content of modifying maleic or citraconic.anhydride is greater than 2%, such as up to can be used in admixturewith unmodified butadiene polymer in an amount such that the totalcontent of the acid anhydride does not exceed 2% based on the totalweight of the butadiene polymer and preferably is no greater than about1% on this basis.

The preferred butadiene polymers are oily liquid polymers having anaverage molecular weight ranging from about 1000 to about 5000.Satisfactory coatings can also be prepared from butadiene polymershaving an average molecular weight ranging from about 700 to about20,000. Higher molecular weight polymers are operative in the practiceof the invention, but the non-volatile content of the resulting coatingcomposition is too low at conventional application viscosity forpractical use, particularly where it is desirable to apply an adequatelyprotective coating weight in a single coat. v 'The liquid coatingcompositions of this invention can be satisfactorily applied byconventional means at a non-volatile content as high as 70% by weight.While the primary utility of these products in the container fieldrequires a substantially high non-volatile content at applicationviscosity to provide a preferred dry coating weight of about 2 to '8milligrams per square inch (if-surface in a single coat, the productscan contain as little as "10% non-volatile content and be recognized aspractical where application by a plurality of coats is acceptable.

A wide variety of substantially non-volatile, organicsolvent-solubleorganic derivatives of titanium are useful in modifying the butadienepolymer in the practice of this invention. Ordinarily at least 1% of theorganic titanium derivative based on the weight of thebutadiene polymeris required to register a practical improvement in the properties of thecoating derived from the butadiene polymer. No significant advantageswere found in using more than 10% by weight of the organic titaniumderivative based on the weight of the butadiene polymer although noadverse effects were observed when the concentration was as high as byweight on the indicated basis. A concentration in the range of about1.5% to 6.0% based on the weight of the butadiene polymer is preferred.

"=Ifetra(2-et-hylhexyl) orthotitanate is a particularly preferred memberof the group of substantially non-volatile orthotitanate esters ofaliphatic monohydric alcohols useful in the practice of this invention.Any of the orthotitanate esters of 6 to carbon atom aliphatic monohydricalcohols can be used in place of the preferred '2-ethylhexylorthotitanate. Volatility of the lower esters, such as the titanateesters of ethyl, isopropyl, butyl or amyl alcohol is too significant forsatisfactory use as the sole organic titanium derivative in theinvention compositions. However, these volatile esters can be present inminor proportions in admixture with the substantially non-volatileorganic titanium derivatives.

Orthotitanate esters of 2-ethylhexanediol-l,3 are particularly preferredamong the titanium chelates useful in the practice of this invention.Qtheruseful titanium chelates can be prepared following the teachings ofBostwick U. S. Patent 2,643,262 where these chelates are prepared byalcoholysis of a tetraorthotitanate ester of a lower alcohol with a 2,3diorgano-1,3 diol haying the ssn l ormu a where ;R and R are ,alkylhydrocarbon radicals whereof the sum of {the carbon atoms in R and Rtotal from 3 to 7 carbon atoms.

. These chelated titaniprn deriyativescan ,be formed in situ in theliquid coatin Qmposition by .alcoholysis chelating beta-ketoacid estersare of the general formula:

Ii H xec-cmo0.Y which is enolizable to;

X-( :=oH( i.oY v where X and Y are each saturated hydrocarbon radicalshaving from 1 to 6 carbonatoms, X and Y being alike or different.Typical beta-ketoacid esters useful in the alcoholysis reaction includefor example the methyl, ethyl, propyl, butyl, ,amyl, hexyl, and,cyclohexyl alcohol esters of acetoaceti-c acid '(beta-oxmbutyric acid),betaoxo-valeric acid, beta-oxo-caproic acid, beta-oxo-caprylic acid, andbeta-oxo-cyclohexanepropionic acid.

Isopropoxy titanium oleate and similar liquid titanium acylates arepreferred among the useful titanium acylates of fatty oil acids. Theliquid titanium acylates offer the advantage of being easily mixed withthe butadiene polymer solution as compared with thewaxy solid titaniumacylates. The titanium acylates can be either monomeric or polymericmaterials prepared by reacting a monomeric or polymeric orthotitanateester of a lower alcohol with an 8 to 20 carbon atom fatty acid asdescribed in Langkarnmerer U. 5. Patent 2,621,193 Haslam 2,621,195 andBoyd 2,666,772. Titanium acylates are also referred to as titanium esteranhydrides in which-the orthotitanic acid is partially anhydrided withthe fatty acid and partially .esterified with a .monohydric alcohol. Thepreferred titanium acylates useful in this invntion are of this lattertype and are .chatacterized by the gen- H General Formula B where R" isa hydrocarbon radical of a lower aliphatic monohydric alcohol such'asisopropyl alcohol or butyl alcohol, and the radical R"CO is the fattyacid acyl radical. x is a digit ordinarily iii the range of l to 100,the average molecular weight of the polymeric titanium acylateordinarilyranging up to about 40,000. Titanium derivatives of General Formula Bare obtained from a product of General Formula A by hydrolysis. Titaniumacylates of General Formula A can also be subjected to alcoholysis forreplacement of the R" group with a hydrocarbon radical having a largernumber of carbon atoms to provide a still greater variety of usefultitanium acylates. In addition to the isopropoxy titanium oleate, usefulpolymeric and monomeric titanium acylates include butoxy titaniumoleate, isopropoxyand butoxy-titanium acylates of lauric acid, coconutoil acids, soya oil acids, linseed oil acids, castor oil acids and talloilacids.

Volatile inert organic mutual solvents for the butadiene polymer and theorganic titanium derivative are preferably hydrocarbon solvents. Any ofthe volatile aromatic hydrocarbons, aliphatic hydrocarbons and mixturesthereof-which ordinarily have a boiling range within the limits of about80 C. to about 220 C. and are used in conventional varnish and paintformulations can be used as the solvent in the liquid coatingcompositions of this invention and as diluents for adjusting thecompositions to a desired application consistency. For economicalreasons, mineral spirts, V. M. and P. naphtha, and petroleum naphthasare ordinarily preferred over the aromatic solvents such as toluol andXylol. Alcohols, esters, ketones and other conventional volatilecompatible organic solvents can be used in admixture with thehydrocarbon solvents whe're these modifying volatile diluents serve adesirable function. It is preferred that the solvent or diluent besubstantially free from water as many of the organic-solvent-solubletitanium derivatives are susceptible to hydrolysis.

For the primary utility of the coating compositions of this invention,the compositions are ordinarily clear unpigmented products. However, forgeneral use the coating'compositions can be pigmented with any of thepigments, extenders, fillers, lakes and dyes used in the for mulation ofconventional varnishes, enamels and paints. These pigmented compositionscan ordinarily contain as much as equal amounts by weight of pigment andbuta diene polymer binder. Presence of a small amount of zincoxidepigment is particularly desirable in the coating compositions used tocoat containers for pork and corn because it serves as a sequesteringagent for sulfur which may be liberated- .from these processed foodproducts to cause sulfurstaining in the absence of an adequatesequestering agent. a.

The coating compositions can also advantageously contain still otherfunctional modifiers, such as metal driers which are used inconventional varnishes to control the rate of cure and liquid siloxanepolymers which serve to alter the surface characteristics of the appliedcoating, particularly to improve the wetting of the metal substrate bythe liquid coating composition to prevent eye-holing. While for use ininteriorly coating of containers, the dry coating preferably consistsessentially of the butadiene polymer modified with the effectivetitanium derivatives, the coating compositions for general utility canalso contain compatible resins and plasticizers in minor proportions.The trialkyl .orthophosphates, particularly tri-2- ethylhexyl-phosphate,were found to be excellent flexibilizers and when used in the range ofabout 1% to 5% based on the weight of the butadiene polymer were foundto advantageously improve the cure.

In applying the invention compositions to ferrous metal substrates, suchas tin-plated sheet steel, sheet steel, terneplate and aluminum cladsteel, the coating after substantial volatile loss of solvent is curedby heating the coated substrate preferably at an approximatetemperatureof 385 F. for a period of 5 to 15 minutes. Other tempera tures in therange of 250 F. to 420 F. can be used to equivalently cure the coatingsby correspondingly altering the heating or baking period in the range ofabout 60 to 5 minutes. A curing temperature as low as about 200 F. isoperative but a long curing time at this temperature ordinarily isimpractical. for commercial operations. Use of curing temperatures above420 F. up to the decomposition temperature does not permit a significantreduction in curing time below the indicated 5 minutes preferredminimum. In the presence of metallic driers, the coatings will air-dryor cure to a tack-free state, but thecoatings are preferably cured bybaking. Heating can be accomplished by any of the conventional meansused in the coating industry.

. The liquid coating compositions can be applied by any oftheconventional methods employed by the coating industry. However, forcoating of sheet metal used in con taine r fabrication, roller coatingis a preferred method as thedesired coating weight is easily andconveniently applied in a single coat and the liquid coating can beapplied at a non-volatile content as high as about 70% by weight. Forgeneral coating purposes spraying, dipping and flow-coating are alsouseful methods of application.

The preferred coating weight for coating ferrous metal sheet substrateswith an adequately protective organic coating for use as an interiorcoating of containers used in the packaging of Wet-pack food products isin the range of 2 to 8 milligrams of dry coating per square inch ofsurface. At coating weights lower than 2 milligrams per square inch thecoating ordinarily is not sufficiently. pro tective and not adequatelyfracture-resistant to either the mechanical operations of containerfabrication or the con-1 ditions associated with heat-processing foodproducts in direct contact with the coating on the interior surface ofthe container. No significant advantages are recognized in applying asan interior coating for food containers fabricated from tin-plated sheetsteel a coating weight greater than 8 milligrams per square inch ofsurface.

Coating weights greater than 8 milligrams per square inch can be usedwhen the clear or pigmented products serve as a general purposedecorative and protective coating applied either as a single coat or asmultiple coats to a ferrous metal substrate. In the general utility ofthe coatings, they can represent either the entire surface coating onthe substrate or at least one layer of a composite surface coatingconsisting of a plurality of layers. For example, the coating can beapplied as the primer coat directly on the substrate and at least oneconventional top-coat finish applied thereover or a conventional coatingcan be used as the undercoat with the invention composition used as thetop-coat finish.

While the primary process of the invention relates to precoating aferrous metal sheet with a coating composition comprising butadienepolymer modified with selected organic derivatives of titanium, andthereafter fabricat ing the precoated metal as a container, the coatingcompositions can also be used to interiorly coat containersprefabricated from uncoated metal parts. The coating compositions canalso be used as a top-coat over the metal substrate precoated with aprimer. When the coating composition is applied to the interior surfaceof prefabricated metal containers, it ordinarily is applied by spraying.

Use of these modified butadiene polymer coating compositions provide adesirable advance in the art of fabricating interiorly coated metalcontainers, particularly those containers used in the packaging ofwet-pack food products which are heat-processed in the container andaqueous alcoholic beverages which are pasteurized in the. container andstored therein for lengthy periods of time. Improved flexibility andsuperior fracture-resistance of the cured coating on a ferrous sheetmetal substrate at a conventional protective coating weight coupled withphysical and chemical resistance of the coating to aqueous extracts ofwet-pack food products heat-processed in direct contact with theprotective organic coating on the interior surface of the containerprovides an advantageously improved container for the food and beveragecanning industry.

While there are disclosed above but a limited number of embodiments ofthe coating compositions, processes and'products of the invention, it ispossible to produce still other embodiments without departing from theinventive concept herein disclosed, and it is desired therefore thatonly such limitations be imposed on the appended claims as are statedtherein or required by the prior art.

The embodiments of this invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A coating composition consisting essentially of (A) at least one oilybutadiene polymer characterized by m average molecular weight from about700 to about 20,000 Selected from theclass consisting of 1) homopolymersof butadiene-1,3, (2) copolymers of butadiene-1,3 and styrene having atleast 75% by weight of copolymerized units of butadiene 1,3 and (3) saidhomopolymers and said copolymers modified with an anhydride of anunsaturated diearboxylic acid selected from the .class consisting ofmaleic anhydride and citraconic anhydride in an amount up to 2% based onthe weight of said polymers, and (B) at least one substantiallynon-volatile organic-solvent-soluble organic derivative of titaniumselected from the class consisting of (1) orthotitanate esters ofaliphatic monohydric alcohols, (2) orthotitanate esters of 2,3diorgano-substituted 1,3 diols, (3) orthotitanate esters of enolizablebeta-ketoacid esters and (4) titanium acylates of fatty oil acids, theproportion of (B) being from about 1% to about 15% based on the weightof said component (A).

2. A liquid coating composition consisting essentially of (A) at leastone oily butadiene polymer characterized by an average molecular weightfrom about 700 to about 20,000 selected from the class consisting of (1)homopolymers of butadiene-1,3, (2) copolymers of butadiene- 1,3 andstyrene having at least 75 by weight of copolymerized units of butadiene1,3 and (3) said homopolymers and said copolymers modified with ananhydride of an unsaturated dicarboxylic acid selected from the classconsisting of maleic anhydride and citraconic anhydride in an amount upto 2% based on the Weight of said polymers, and (B) at least onesubstantially nonvolatile organic-solvent-soluble organic derivative oftitanium selected from the class consisting of (l) orthotitanate estersof aliphatic monohydric alcohols, (2) orthotitanate esters of 2,3diorgano-substituted 1,3 diols, (3) orthotitanate esters, of enolizablebeta-ketoacid esters and (4) titanium acylates of fatty oil acids, and(C) a volatile liquid organic solvent for (A) and (B) characterized by aboiling temperature from about 80 C. to about 220 F., the proportion ofsaid component (B) being from about 1% to about 15% based on the Weightof said component (A) and the total non-volatile content being in therange of about to about 70% based on the total weight of the liquidcomposition.

3. The coating composition of claim 1 in which (B) the organicderivative of titanium is tetra(2-ethylhexyl) orthotitanate.

4. The coating composition of claim 1 in Which (B) the organicderivative of titanium is the orthotitanate ester of2-ethylhexanediol-1,3.

5. The coating composition of claim 1 in which (B) the organicderivative of titanium is the orthotitanate ester of ethylacetoacetate.

6. The coating composition of claim 1 in which (B) the organicderivative of titanium is polymeric isopropoxytitanium oleate.

7. The coating composition of claim 1 in which (A) the butadiene polymeris a homopolymer of butadiene- 1,3.

8. The coating composition of claim 1 in which (A) the butadiene polymeris a copolymer of butadiene-1,3 and styrene having at least 75 by weightof copolymerized units of butadiene 1,3.

9. The coating composition of claim 1 in which (A) the butadiene polymeris a butadiene homopolymer modified with up to 2% by weight of maleicanhydride;

terized by an averag meolecular weight from about 700' to about 20,000selected from the class consisting of (1) 14 homopolymers of butadiene-1,3, (2) copolymers of buta diene-l,3 and styrene having at least 75% byweight of copolymerized units of butadiene 1,3, and (3).said'homopolymers and said copolymers modified with an anhydride of anunsaturated dicarboxylic acid selected from the class consisting ofmaleic anhydride and citraconic anhydride in an amount up to'2% byweight of said .polymers, with (B) at least one substantiallynon-volatile organic-solvent-soluble organic derivative of titaniumselected from the class consisting of (1) orthotitanate esters ofaliphatic ,monohydricalcohols, (2) orthotitanate esters of 2,3diorgano-substituted' 1,3 diols, (3) orthotitanate esters of enolizablebeta-ketoacid esters and (4) titanium acylates of fatty oil acids, inthe presence of (C) a volatile liquid organic solvent for (A) and (B)characterized by a boiling temperature from about C. to about 220 C.,the proportion of said component (B) being from about 1% to about 15%based on the weight of said component (A), and the total non-volatilecontent being in the range of about 10% to about 70% based on the totalweight of the liquid composition.

12. A process of preparing a formable organic-coated sheet metalsubstrate designed for use as a component part of a packaging containerwhich comprises applying to at least one surface of a thin sheet metalsubstrate a thin coat of the liquid coating composition of claim 2, inan amount corresponding to a dry coating weight of from 2 to about 8milligrams per square inch of substrate surface, drying said coating byvolatile loss of solvent therefrom and curing the resulting coating byheating under conditions corresponding from about 60 minutes at 250 F.to 5 minutes at about 420 F.

13. In the process of manufacturing metal packaging containers involvingfabrication of interiorly coated containers from container parts stampedfrom a ferrous metal sheet precoated with a cured organic coating whichshall constitute the interior coating of the container, the improvementwhich consists of the steps of applying to at least one surface of themetal sheet a sufiicient amount of the coating composition of claim 2 toprovide a dry coating weight of about 2 to 8 milligrams per square inchof coated surface, drying the coating'by partial loss of the volatileorganic solvent therefrom, and heating the coated metal sheet at atemperature in the range of about 250 F. to about 420 F. for a period oftime ranging from about 60 minutes to about 5 minutes to effect a degreeof cure substantially equivalent to heating the coated substrate at 385F. for 5 to 15 minutes.

14. The improved process of claim 13 in which said coating compositionconsists essentially of (A) a homopolymer of butadiene-1,3 having amolecular weight in the range of 1000 to 5000, (B) about 1.5% to about6.0%, based on the weight of (A), of tetra(2-ethylhexyl) orthotitanate,and (C) a volatile hydrocarbon solvent for (A) and (B) having a boilingrange within the limits of about 80 C. and about 220 C.

15. A thin formable flat ferrous metal sheet, designed for stamping intoprecoated container parts, having a baked coating of the product ofclaim 1 on at least one surface thereof in an amount from 2 to about 8milligrams per square inch of coated surface.

16. A container comprising a ferrous sheet metal cylindrical body partprovided with at least one ferrous sheet metal end-closure sealed tosaid cylindrical body, the inner surfaces of said container having abaked coating of the product of claim 1 at a dry coating weight of from2 milligrams to about 8 milligrams per square inch of coated surface.

17. A container comprising a ferrous sheet metal cylindrical body parthaving a baked coating of the product of claim 1 on the interior surfacethereof provided with at least one ferrous sheet metal end-closuresealed thereto, said end-closure having a baked coating of the productof claim 1 on the surface corresponding 15 16 to an interior surface ofsaid container, said body part 2,680,108 j Schmidt June 1, 1954 and saidend-closure each having said coating at a dry 2,777,826 Olson Ian. 15,1957 coating weight of from 2 to about 8 milligrams per square FOREIGN Tinch of coated metal surface, said ferrous metal of said body part andsaid end closure being tin-plated sheet steel 5 125,450 Australia Sept-1947 have a coating of tin in an amount of .25 to 1 5 pounds OTHERREFERENCES 7 of t n per 218 square feet of surface area of said ferrousDu Pont Titanium Organics, Titanium Acylatess,

ssad- 15004043, E. I. du Pont de Nemours and 00.,

References Cited in the file of this patent 10 UNITED STATES PATENTS2,582,991 Hempel Ian. 22, 1952

1. A COATING COMPOSITION CONSISTING ESSENTIALLY OF (A) AT LEAST ONE OILYBUTADIENE POLYMER CHARACTERIZED BY AN AVERAGE MOLECULAR WEIGHT FROMABOUT 700 TO ABOUT 20,000 SELECTED FROM THE CLASS CONSISTING OF (1)HOMOPOLYMERS OF BUTADIENE-1,3, (2) COPOLYMERS OF BUTADIENEN-1,3 ANDSTYRENE HAVING AT LEAST 75% BY WEIGHT OF COPOLYMERIZED UNITS OFBUTADIENE 1,3 AND: (3) SAID HOMOPOLYMERS AND SAID COPOLYMERS MODIFIEDWITH AN ANHYDRIDE OF AN UNSATURATED DICARBOXYLIC SELECTED FROM THE CLASSCONSISTING OF MALERIC ANHYDRIDE AND CITRACONIC ANHYDRIDE IN AN AMOUNT UPTO 2% BASED ON THE WEIGHT OF SAID POLYMERS, AND (B) AT LEAST ONESUBSTANTIALLY NON-VOLATILE ORGANIC-SOLVENT-SOLUBLE ORGAINC DERVATIVE OFTITANIUM SELECTED FROM THE CLASS CONSISTING OF (1) ORTHOTITANATE ESTERSOF ALIPHATIC MONOHYDRIC ALCOHOLS, (2) ORTHOTITANATE ESTERS OF 2,3DIORGANO-SUBSTITUTED 1,3 DIOLS, (3) ORTHOTITANATE ESTERS OF ENOLIZABLEBETA-KETOACID ESTERS AND (4) TITANIUM ACYLATED OF FATTY OIL ACIDS, THEPROPORTION OF (B) BEING FROM ABOUT 1% TO ABOUT 15% BASED ON THE WEIGHTOF SAID COMPENENT (A).
 16. A CONTAINER COMPRISING A FERROUS SHEET METALCYLINDRICAL BODY PART PROVIDED WITH AT LEAST ONE FERROUS SHEET METALEND-CLOSURE SEALED TO SAID CYLINDRICAL BODY, THE INNER SURFACES OF SAIDCONTAINER HAVING A BAKED COATING OF THE PRODUCT OF CLAIM 1 AT A DRYCOATING WEIGHT OF FROM 2 MILLIGRAMS TO ABOUT 8 MILLIGRAMS PER SQUAREINCH OF COATING SURFACE.